Pin nightly to avoid regression

Manishearth · Manishearth · commit d456e2b10896 · 2019-07-11T09:36:28.000-07:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,7 +1,7 @@
 language: rust
 
 rust:
-  - nightly
+  - nightly-2019-07-06
   - stable
 
 before_script:
